1. Field of the Invention
The present invention relates to a recording medium for business machines suitable for recording with ink, and to a process of production of the recording medium. In particular, the present invention relates to a recording medium for business machines which is excellent in ink receptability, sharpness of recorded color images, water-resistance, light-fastness, and anti-blocking property, and to a process for producing the recording medium.
The present invention also relates to an ink-jet recording method employing the above recording medium.
2. Related Background Art
The ink-jet recording is attracting attention because of less noise, and capability of high-speed and multi-color printing. The ink-jet recording is a method in which droplets of an ink (or a recording liquid) are formed and ejected by an electrostatic attraction, a mechanical vibration or displacement caused by a piezoelectric element, or pressure caused by heating and foaming, or the like to deposit a part or whole of the ink on a recording medium such as a paper sheet.
The recording medium for the business machines includes recording mediums for copying machines and printers of ink-jet type, electrophotography type, thermal transfer type, ink ribbon type, sublimation transfer type, and so forth.
The ink for ink-jet recording contains water as the main component in view of safety and recording characteristics, and frequently contains additionally a polyhydric alcohol for the purpose of prevention of orifice clogging and improvement of ejection stability.
Hitherto, plain paper sheets, or recording media called ink-jet recording paper having a porous ink-receiving layer on a substrate have been used for ink-jet recording. With improvement for high-speed recording and multi-color printing and propagation of use of ink-jet recording, the ink-jet recording medium is required to have further improved properties for wider application range. The ink-jet recording medium is demanded to satisfy the basic requirements as shown below for obtaining recording mediums of higher resolution and higher quality of recorded images:
(1) the recording medium accepts rapidly the ejected ink, PA1 (2) the accepted ink does not flow into the later accepted ink when the ink dots become superposed, PA1 (3) the ink does not diffuse excessively on the recording medium in order to prevent undesired enlargement of ink dot diameters, PA1 (4) the ink dots on the recording medium are nearly in a complete circle shape, and have smooth perimeter, and PA1 (5) the ink dots give high OD (optical density), and sharp perimeter. PA1 (6) color-developing properties is excellent at the ink-deposited portion of the recording medium, PA1 (7) ink fixation is particularly excellent (because ink droplets in the same number of ink as the number of ink color may possibly superposed on the same spot. PA1 (8) the recording medium has gloss at the surface, PA1 (9) the recording medium has high whiteness or high transparency, PA1 (10) the recording medium and the image formed thereon has high water-resistance, PA1 (11) the recorded image has high light-fastness, and PA1 (12) the surface does not become sticky even at a high temperature and a high humidity, and exhibits high anti-blocking properties.
In multi-color ink-jet recording, the recording medium is demanded to satisfy further the requirements below in addition to the above requirements (1) to (5):
The recorded images formed by ink-jet recording have been used only for surface image observation. However, with improvement and propagation of ink-jet recording apparatuses, recording media are required to be suitable also for image observation other than the surface observation. For example, recording media are required to be suitable for observation of images projected on a screen or the like by use of an optical device such as a lantern slide and an OHP (overhead projector); color separation filters for preparing a positive plate of color printing; a CMF (color mosaic filter) for color display by use of liquid crystal; and so forth.
In the recording medium used for surface image observation, the diffused light from the recorded image is mainly observed, while in the recording mediums for non-surface image observation, transmitted light is mainly observed. Therefore, the recording medium for non-surface image observation is required to have high light-transmissivity (especially, linear light transmittance) in addition to the above-described general requirements on ink-jet recording medium.
Nevertheless, no recording medium has been obtained which satisfies all of the above requirements at the moment.
Most of the recording media for surface image observation have a porous inorganic ink-receiving layer on the surface, and the ink is received and fixed in the voids of the pores. Such a recording medium, because of the porosity of the surface, does not have gloss, and needs to have a certain thickness of the ink-receiving layer for absorption of ink. On the other hand, another type of recording medium, which has a non-porous and water-soluble resin layer as the ink-receiving layer on the surface, has disadvantages that involatile materials such as polyhydric alcohol in the ink remains at the surface of the recording medium for a long time to delay drying and fixing of the ink, thereby causing staining of clothes, peeling of the layer, and impairment of the recorded image.